Download Lactose Intolerance What is lactose intolerance?

Lactose
Intolerance
National Digestive Diseases Information Clearinghouse
What is lactose intolerance?
U.S. Department
of Health and
Human Services
NATIONAL
INSTITUTES
OF HEALTH
Lactose intolerance is the inability or insuf­
ficient ability to digest lactose, a sugar found
in milk and milk products. Lactose intoler­
ance is caused by a deficiency of the enzyme
lactase, which is produced by the cells lining
the small intestine. Lactase breaks down
lactose into two simpler forms of sugar
called glucose and galactose, which are then
absorbed into the bloodstream.
Not all people with lactase deficiency have
digestive symptoms, but those who do may
have lactose intolerance. Most people
with lactose intolerance can tolerate some
amount of lactose in their diet.
People sometimes confuse lactose intoler­
ance with cow milk allergy. Milk allergy is a
reaction by the body’s immune system to one
or more milk proteins and can be life threat­
ening when just a small amount of milk or
milk product is consumed. Milk allergy most
commonly appears in the first year of life,
while lactose intolerance occurs more often
in adulthood.
What causes lactose
intolerance?
The cause of lactose intolerance is best
explained by describing how a person devel­
ops lactase deficiency.
Primary lactase deficiency develops over time
and begins after about age 2 when the body
begins to produce less lactase. Most children
who have lactase deficiency do not experi­
ence symptoms of lactose intolerance until
late adolescence or adulthood.
Stomach
Liver
Large
intestine
Small
intestine
Appendix
Anus
The digestive tract.
Researchers have identified a possible
genetic link to primary lactase deficiency.
Some people inherit a gene from their par­
ents that makes it likely they will develop pri­
mary lactase deficiency. This discovery may
be useful in developing future genetic tests to
identify people at risk for lactose intolerance.
Secondary lactase deficiency results from
injury to the small intestine that occurs
with severe diarrheal illness, celiac disease,
Crohn’s disease, or chemotherapy. This type
of lactase deficiency can occur at any age but
is more common in infancy.
Who is at risk for lactose
intolerance?
How is lactose intolerance
diagnosed?
Lactose intolerance is a common condition
that is more likely to occur in adulthood,
with a higher incidence in older adults.
Some ethnic and racial populations are
more affected than others, including African
Americans, Hispanic Americans, American
Indians, and Asian Americans. The condi­
tion is least common among Americans of
northern European descent.
Lactose intolerance can be hard to diagnose
based on symptoms alone. People may think
they suffer from lactose intolerance because
they have digestive symptoms; however,
other conditions such as irritable bowel syn­
drome can cause similar symptoms.
Infants born prematurely are more likely to
have lactase deficiency because an infant’s
lactase levels do not increase until the third
trimester of pregnancy.
What are the symptoms of
lactose intolerance?
People with lactose intolerance may feel
uncomfortable 30 minutes to 2 hours after
consuming milk and milk products. Symp­
toms range from mild to severe, based on the
amount of lactose consumed and the amount
a person can tolerate.
Common symptoms include
• abdominal pain
• abdominal bloating
• gas
• diarrhea
• nausea
After taking a medical history and perform­
ing a physical examination, the doctor may
first recommend eliminating all milk and
milk products from the person’s diet for a
short time to see if the symptoms resolve.
Tests may be necessary to provide more
information.
Two tests are commonly used to measure the
digestion of lactose.
Hydrogen Breath Test. The person drinks a
lactose-loaded beverage and then the breath
is analyzed at regular intervals to measure
the amount of hydrogen. Normally, very
little hydrogen is detectable in the breath,
but undigested lactose produces high levels
of hydrogen. Smoking and some foods and
medications may affect the accuracy of the
results. People should check with their doc­
tor about foods and medications that may
interfere with test results.
Stool Acidity Test. The stool acidity test is
used for infants and young children to mea­
sure the amount of acid in the stool. Undi­
gested lactose creates lactic acid and other
fatty acids that can be detected in a stool
sample. Glucose may also be present in the
stool as a result of undigested lactose.
Because lactose intolerance is uncommon
in infants and children younger than 2, a
health professional should take special care
in determining the cause of a child’s digestive
symptoms.
2 Lactose Intolerance
How is lactose intolerance
managed?
Although the body’s ability to produce
lactase cannot be changed, the symptoms
of lactose intolerance can be managed with
dietary changes. Most people with lactose
intolerance can tolerate some amount of
lactose in their diet. Gradually introducing
small amounts of milk or milk products may
help some people adapt to them with fewer
symptoms. Often, people can better tolerate
milk or milk products by taking them with
meals.
The amount of change needed in the diet
depends on how much lactose a person can
consume without symptoms. For example,
one person may have severe symptoms after
drinking a small glass of milk, while another
can drink a large glass without symptoms.
Others can easily consume yogurt and hard
cheeses such as cheddar and Swiss but not
milk or other milk products.
The Dietary Guidelines for Americans 2005
recommend that people with lactose intoler­
ance choose milk products with lower levels
of lactose than regular milk, such as yogurt
and hard cheese.
Lactose-free and lactose-reduced milk and
milk products, available at most supermar­
kets, are identical to regular milk except that
the lactase enzyme has been added. Lactosefree milk remains fresh for about the same
length of time or longer than regular milk
if it is ultra-pasteurized. Lactose-free milk
may have a slightly sweeter taste than regular
milk. Soy milk and other products may be
recommended by a health professional.
People who still experience symptoms after
dietary changes can take over-the-counter
lactase enzyme drops or tablets. Taking the
tablets or a few drops of the liquid enzyme
3 Lactose Intolerance
when consuming milk or milk products may
make these foods more tolerable for people
with lactose intolerance.
Parents and caregivers of a child with lac­
tose intolerance should follow the nutrition
plan recommended by the child’s doctor or
dietitian.
Lactose Intolerance and
Calcium Intake
Milk and milk products are a major source
of calcium and other nutrients. Calcium is
essential for the growth and repair of bones
at all ages. A shortage of calcium intake in
children and adults may lead to fragile bones
that can easily fracture later in life, a condi­
tion called osteoporosis.
The amount of calcium a person needs to
maintain good health varies by age. Recom­
mendations are shown in Table 1.
Table 1. Recommended calcium intake by
age group
Age group
Amount of calcium
to consume daily,
in milligrams (mg)
0–6 months
210 mg
7–12 months
270 mg
1–3 years
500 mg
4–8 years
800 mg
9–18 years
1,300 mg
19–50 years
1,000 mg
51–70+ years
1,200 mg
Source: Adapted from Dietary Reference Intakes, 2004, Institute of Medicine, National Academy of Sciences.
Women who are pregnant or breastfeeding
need between 1,000 and 1,300 mg of calcium
daily.
Getting enough calcium is important for
people with lactose intolerance when the
intake of milk and milk products is limited.
Many foods can provide calcium and other
nutrients the body needs. Non-milk products
that are high in calcium include fish with soft
bones such as salmon and sardines and dark
green vegetables such as spinach.
Table 2 lists foods that are good sources of
dietary calcium.
Yogurt made with active and live bacterial
cultures is a good source of calcium for many
people with lactose intolerance. When this
type of yogurt enters the intestine, the bacte­
rial cultures convert lactose to lactic acid,
so the yogurt may be well-tolerated due to
a lower lactose content than yogurt without
live cultures. Frozen yogurt does not contain
bacterial cultures, so it may not be welltolerated.
Calcium is absorbed and used in the body
only when enough vitamin D is present.
Some people with lactose intolerance may
Table 2. Calcium content in common foods
Non-milk Products
Calcium Content
Rhubarb, frozen, cooked, 1 cup
348 mg
Sardines, with bone, 3 oz.
325 mg
Spinach, frozen, cooked, 1 cup
291 mg
Salmon, canned, with bone, 3 oz.
181 mg
Soy milk, unfortified, 1 cup
61 mg
Orange, 1 medium
52 mg
Broccoli, raw, 1 cup
41 mg
Pinto beans, cooked, 1/2 cup
40 mg
Lettuce greens, 1 cup
20 mg
Tuna, white, canned, 3 oz.
12 mg
Milk and Milk Products
Yogurt, with active and live cultures, plain, low-fat,
vitamin D-fortified, 1 cup
415 mg
Milk, reduced fat, vitamin D-fortified, 1 cup
285 mg
Swiss cheese, 1 oz.
224 mg
Cottage cheese, 1/2 cup
87 mg
Ice cream, 1/2 cup
84 mg
Source: Adapted from U.S. Department of Agriculture, Agricultural Research Service. 2008. USDA National
Nutrient Database for Standard Reference, Release 21.
4 Lactose Intolerance
not be getting enough vitamin D. Vitamin D
comes from food sources such as eggs, liver,
and vitamin D-fortified milk and yogurt.
Regular exposure to sunlight also helps the
body naturally absorb vitamin D.
• processed meats, such as bacon, sau­
sage, hot dogs, and lunch meats
Talking with a doctor or registered dieti­
tian may be helpful in planning a balanced
diet that provides an adequate amount
of nutrients—including calcium and
vitamin D—and minimizes discomfort. A
health professional can determine whether
calcium and other dietary supplements are
needed.
• liquid and powdered milk-based meal
replacements
What other products contain
lactose?
Milk and milk products are often added
to processed foods—foods that have been
altered to prolong their shelf life. People
with lactose intolerance should be aware of
the many food products that may contain
even small amounts of lactose, such as
• margarine
• salad dressings
• protein powders and bars
• candies
• non-dairy liquid and powdered coffee
creamers
• non-dairy whipped toppings
Checking the ingredients on food labels is
helpful in finding possible sources of lactose
in food products. If any of the following
words are listed on a food label, the product
contains lactose:
• milk
• lactose
• whey
• bread and other baked goods
• curds
• waffles, pancakes, biscuits, cookies, and
mixes to make them
• milk by-products
• processed breakfast foods such as
doughnuts, frozen waffles and pancakes,
toaster pastries, and sweet rolls
• non-fat dry milk powder
• processed breakfast cereals
• instant potatoes, soups, and breakfast
drinks
• potato chips, corn chips, and other pro­
cessed snacks
5 Lactose Intolerance
• dry milk solids
Lactose is also used in some prescription
medicines, including birth control pills, and
over-the-counter medicines like products to
treat stomach acid and gas. These medicines
most often cause symptoms in people with
severe lactose intolerance.
Points to Remember
• Lactose intolerance is the inability or
insufficient ability to digest lactose, a
sugar found in milk and milk products.
• Lactose intolerance is caused by a
deficiency of the enzyme lactase, which
is produced by the cells lining the small
intestine.
• Not all people with lactase deficiency
have digestive symptoms, but those
who do may have lactose intolerance.
• Most people with lactose intolerance
can tolerate some amount of lactose in
their diet.
• People with lactose intolerance may
feel uncomfortable after consuming
milk and milk products. Symptoms
can include abdominal pain, abdomi­
nal bloating, gas, diarrhea, and nausea.
• The symptoms of lactose intolerance
can be managed with dietary changes.
• Getting enough calcium and vitamin D
is a concern for people with lactose
intolerance when the intake of milk
and milk products is limited. Many
foods can provide the calcium and
other nutrients the body needs.
• Talking with a doctor or registered
dietitian may be helpful in planning a
balanced diet that provides an ade­
quate amount of nutrients—including
calcium and vitamin D—and mini­
mizes discomfort. A health profes­
sional can determine whether calcium
and other dietary supplements are
needed.
• Milk and milk products are often added to processed foods. Check­
ing the ingredients on food labels is helpful in finding possible sources of lactose in food products. 6 Lactose Intolerance
Hope through Research
The National Institute of Diabetes and
Digestive and Kidney Diseases’ (NIDDK’s)
Division of Digestive Diseases and Nutri­
tion conducts and supports basic and clinical
research into digestive disorders.
Participants in clinical trials can play a more
active role in their own health care, gain
access to new research treatments before
they are widely available, and help others by
contributing to medical research. For infor­
mation about current studies, visit
www.ClinicalTrials.gov.
For More Information
American Dietetic Association
120 South Riverside Plaza, Suite 2000
Chicago, IL 60606–6995
Internet: www.eatright.org
International Foundation for Functional
Gastrointestinal Disorders
P.O. Box 170864
Milwaukee, WI 53217–8076
Phone: 1–888–964–2001 or 414–964–1799
Fax: 414–964–7176
Email: [email protected]
Internet: www.iffgd.org
Acknowledgments
Publications produced by the Clearinghouse
are carefully reviewed by both NIDDK
scientists and outside experts. This publica­
tion was originally reviewed by Eric Sibley,
M.D., Ph.D., Stanford University School
of Medicine. Rachel Fisher, M.S., M.P.H.,
R.D., and Jean Pennington, Ph.D., R.D.,
Division of Nutrition Research Coordina­
tion, NIDDK, reviewed the updated version
of the publication.
7 Lactose Intolerance
You may also find additional information about this
topic by
• searching the NIDDK Reference Collection at
www.catalog.niddk.nih.gov/resources
• visiting MedlinePlus at www.medlineplus.gov
This publication may contain information about
medications. When prepared, this publication
included the most current information available.
For updates or for questions about any medications,
contact the U.S. Food and Drug Administration
toll-free at 1–888–INFO–FDA (1–888–463–6332) or
visit www.fda.gov. Consult your doctor for more
information.
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U.S. DEPARTMENT OF HEALTH
AND HUMAN SERVICES
National Institutes of Health
NIH Publication No. 09–2751
June 2009